U.S. patent number 9,753,430 [Application Number 14/224,223] was granted by the patent office on 2017-09-05 for sensor device having plural resistance change sensors and method of using the same.
This patent grant is currently assigned to Brother Kogyo Kabushiki Kaisha. The grantee listed for this patent is Ryo Ito, Kenji Kanazawa, Osamu Takahashi, Jie Zheng. Invention is credited to Ryo Ito, Kenji Kanazawa, Osamu Takahashi, Jie Zheng.
United States Patent |
9,753,430 |
Zheng , et al. |
September 5, 2017 |
**Please see images for:
( Certificate of Correction ) ** |
Sensor device having plural resistance change sensors and method of
using the same
Abstract
To detect humidity, used are a first series connection circuit
connecting a thermistor and a fixed resistor via a node, a second
series connection circuit connecting a resistance change type
humidity sensor and the thermistor via the node, and a third series
connection circuit connecting the humidity sensor and the fixed
resistor via the node. A predetermined voltage is applied across
the first circuit to detect a first voltage indicating temperature
through the node, and secondly across the second circuit to detect
a second voltage indicating a first humidity through the node, and
finally across the third circuit to detect a third voltage
indicating a second humidity through the node. Then, the first
voltage is compared with a reference voltage and judgment is made,
based on a comparison result, to determine which of the second
voltage and the third voltage is relevant to use as a basis for
outputting the humidity as detected.
Inventors: |
Zheng; Jie (Nagoya,
JP), Ito; Ryo (Nagoya, JP), Kanazawa;
Kenji (Tsukuba, JP), Takahashi; Osamu (Nagoya,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Zheng; Jie
Ito; Ryo
Kanazawa; Kenji
Takahashi; Osamu |
Nagoya
Nagoya
Tsukuba
Nagoya |
N/A
N/A
N/A
N/A |
JP
JP
JP
JP |
|
|
Assignee: |
Brother Kogyo Kabushiki Kaisha
(Nagoya-shi, Aichi-ken, JP)
|
Family
ID: |
51568142 |
Appl.
No.: |
14/224,223 |
Filed: |
March 25, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140283597 A1 |
Sep 25, 2014 |
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Foreign Application Priority Data
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Mar 25, 2013 [JP] |
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2013-062089 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03G
21/203 (20130101); G01N 27/121 (20130101); G03G
2215/00084 (20130101) |
Current International
Class: |
G03G
21/20 (20060101); G01N 27/12 (20060101) |
Field of
Search: |
;73/335.02,335.03,335.05
;399/44,94 ;324/71.1,693,705,712 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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S57-017104 |
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Jan 1982 |
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JP |
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S61-091552 |
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May 1986 |
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JP |
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S61-128149 |
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Jun 1986 |
|
JP |
|
S64-088144 |
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Apr 1989 |
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JP |
|
H03-138553 |
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Jun 1991 |
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JP |
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H05-149905 |
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Jun 1993 |
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JP |
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H06-221882 |
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Aug 1994 |
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JP |
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H07-311169 |
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Nov 1995 |
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JP |
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H08-029370 |
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Feb 1996 |
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JP |
|
H09-005371 |
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Jan 1997 |
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JP |
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2001-147139 |
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May 2001 |
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JP |
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2001-153438 |
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Jun 2001 |
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JP |
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2005-221484 |
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Aug 2005 |
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JP |
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2006-275761 |
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Oct 2006 |
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JP |
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2007-232428 |
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Sep 2007 |
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JP |
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2007-248455 |
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Sep 2007 |
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JP |
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2007-263702 |
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Oct 2007 |
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JP |
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2009-180560 |
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Aug 2009 |
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JP |
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2009-293942 |
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Dec 2009 |
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JP |
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2013-096823 |
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May 2013 |
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JP |
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Other References
JP Office Action dtd Jan. 19, 2010, JP Appln. 2008-018162, English
Translation. cited by applicant.
|
Primary Examiner: Gibson; Randy
Assistant Examiner: Kidanu; Gedeon M
Attorney, Agent or Firm: Banner & Witcoff, Ltd.
Claims
What is claimed is:
1. A sensor device comprising: a first resistance change sensor
having a first terminal and a second terminal and configured to
detect a first parameter; a second resistance change sensor having
a third terminal and a fourth terminal connected to the first
terminal and configured to detect a second parameter different from
the first parameter; a fixed resistor having a fifth terminal and a
sixth terminal connected to both the first terminal and the fourth
terminal; and a controller having a first output port connected to
the second terminal, a second output port connected to the third
terminal, a third output port connected to the fifth terminal, and
an input port connected to all of the first terminal, the fourth
terminal and the sixth terminal, the controller being configured
to: execute a first signal applying process wherein the first
output port is rendered high impedance, and an alternating voltage
is applied across the second output port and the third output port
where the alternating voltage alternately changes between a first
voltage level and a second voltage level different from the first
voltage level, the high impedance being high to substantially be
equivalent to an open circuit, execute a first detection process
wherein a first detection voltage applied to the input port is
detected when the second output port is at one of the first voltage
level and the second voltage level and the third output port is at
remaining one of the first voltage level and the second voltage
level during execution of the first signal applying process,
execute a second signal applying process subsequent to the
execution of the first detection process, wherein one of the second
output port and the third output port is rendered the high
impedance, the alternating voltage is applied across the first
output port and remaining one of the second output port and the
third output port, execute a second detection process subsequent to
the execution of the first detection process, wherein a second
detection voltage applied to the input port is detected when the
first output port is at one of the first voltage level and the
second voltage level and the second output port or third output
port whichever is not rendered the high impedance is at remaining
one of the first voltage level and the second voltage level during
execution of the second signal applying process, and execute a
parameter detection process wherein a value of the first parameter
is determined using the first detection voltage and the second
detection voltage.
2. The sensing device according to claim 1, further comprising a
memory storing a table containing a plurality of sets of data, each
set of data containing a first value equivalent to the first
detection voltage, a second value equivalent to the second
detection voltage and a humidity value, the first value, the second
value and the humidity value in each set being correlated to one
another.
3. The sensor device according to claim 1, wherein the first
resistance change sensor is configured to be driven by an
alternating signal and detect humidity, the first resistance change
sensor having temperature-dependent resistance-versus-humidity
characteristics, wherein the second resistance change sensor
comprises a thermistor, and wherein in the parameter detection
process, the controller is configured to determine a value of
humidity using a resistance-versus-humidity characteristic
corresponding to the first detection voltage related to a
temperature detected in the first detection process, and also using
the second detection voltage related to humidity detected in the
second detection process.
4. The sensor device according to claim 3, wherein in the second
signal applying process, the controller is configured to: render
the third output port the high impedance, apply the alternating
voltage across the first output port and the second output port,
and detect the second detection voltage applied to the input port
as a first humidity indicating voltage, and render the second
output port the high impedance, apply the alternating voltage
across the first output port and the third output port, and detect
the second detection voltage applied to the input port as a second
humidity indicating voltage, and wherein the controller is further
configured to execute a judgment process wherein judgment is made
as to which of the first humidity indicating voltage and the second
humidity indicating voltage is relevant to use in determining the
value of humidity upon comparison of the second humidity indicating
voltage with a threshold voltage.
5. The sensor device according to claim 3, wherein in the second
signal applying process, the controller is configured to: render
the third output port the high impedance, apply the alternating
voltage across the first output port and the second output port and
detect the second detection voltage applied to the input port as a
first humidity indicating voltage, and render the second output
port the high impedance, apply the output voltage across the first
output port and the third output port and detect the second
detection voltage applied to the input port as a second humidity
indicating voltage, and wherein the controller is further
configured to execute a judgment process wherein judgment is made
to determine which of the first humidity indicating voltage and the
second humidity indicating voltage is relevant to use as a basis
for outputting the humidity upon comparison of the first humidity
indicating voltage with a threshold voltage.
6. The sensor device according to claim 5, wherein the first
resistance change sensor operates as a humidity sensor, the
humidity sensor having a resistance characteristic such that
resistance of the humidity sensor decreases as humidity increases,
and the thermistor has a resistance characteristic such that
resistance of the thermistor decreases as temperature increases,
and wherein the controller is further configured to: detect the
first humidity indicating voltage under a condition where the first
output port is at the first voltage level and the second output
port is at the second voltage level lower than the first voltage
level, perform humidity detection using the first humidity
indicating voltage when the first humidity indicating voltage is
greater than the threshold voltage, and perform humidity detection
using the second humidity indicating voltage when the first
humidity indicating voltage is equal to or smaller than the
threshold voltage.
7. The sensor device according to claim 5, wherein the first
resistance change sensor operates as a humidity sensor, the
humidity sensor having a resistance characteristic such that
resistance of the humidity sensor decreases as humidity increases,
and wherein the controller is further configured to: detect the
second humidity indicating voltage under a condition where the
first output port is at the first voltage level and the third
output port is at the second voltage level lower than the first
voltage level, perform humidity detection using the first humidity
indicating voltage when the second humidity indicating voltage is
greater than the threshold voltage, and perform humidity detection
using the second humidity indicating voltage when the first
humidity indicating voltage is equal to or smaller than the
threshold voltage.
8. An image forming device comprising: a sensor device; and an
image forming portion configured to form an image on an object
based on image data, wherein the sensor device includes: a first
resistance change sensor having a first terminal and a second
terminal and configured to detect a first parameter; a second
resistance change sensor having a third terminal and a fourth
terminal connected to the first terminal and configured to detect a
second parameter different from the first parameter; a fixed
resistor having a fifth terminal and a sixth terminal connected to
both the first terminal and the fourth terminal; and a controller
having a first output port connected to the second terminal, a
second output port connected to the third terminal, a third output
port connected to the fifth terminal, and an input port connected
to all of the first terminal, the fourth terminal and the sixth
terminal, the controller being configured to: execute a first
signal applying process wherein the first output port is rendered
high impedance, and an alternating voltage is applied across the
second output port and the third output port where the alternating
voltage alternately changes between a first voltage level and a
second voltage level different from the first voltage level, the
high impedance being high to substantially be equivalent to an open
circuit, execute a first detection process wherein a first
detection voltage applied to the input port is detected when the
second output port is at one of the first voltage level and the
second voltage level and the third output port is at remaining one
of the first voltage level and the second voltage level during
execution of the first signal applying process, execute a second
signal applying process subsequent to the execution of the first
detection process, wherein one of the second output port and the
third output port is rendered the high impedance, the alternating
voltage is applied across the first output port and remaining one
of the second output port and the third output port, execute a
second detection process subsequent to the execution of the first
detection process, wherein a second detection voltage applied to
the input port is detected when the first output port is at one of
the first voltage level and the second voltage level and the second
output port or third output port whichever is not rendered the high
impedance is at remaining one of the first voltage level and the
second voltage level during execution of the second signal applying
process, and execute a parameter detection process wherein a value
of the first parameter is determined using the first detection
voltage and the second detection voltage.
9. The image forming device according to claim 8, wherein the
sensor device further comprises a memory storing a table containing
a plurality of sets of data, each set of data containing a first
value equivalent to the first detection voltage, a second value
equivalent to the second detection voltage and a humidity value,
the first value, the second value and the humidity value in each
set being correlated to one another.
10. The image forming device according to claim 8, wherein the
first resistance change sensor is configured to be driven by an
alternating signal and detect humidity, the first resistance change
sensor having temperature-dependent resistance-versus-humidity
characteristics, wherein the second resistance change sensor
comprises a thermistor, and wherein in the parameter detection
process, the controller is configured to determine a value of
humidity using a resistance-versus-humidity characteristic
corresponding to the first detection voltage related to a
temperature detected in the first detection process, and also using
the second detection voltage related to humidity detected in the
second detection process.
11. The image forming device according to claim 10, wherein in the
second signal applying process, the controller is configured to:
render the third output port the high impedance, apply the
alternating voltage across the first output port and the second
output port, and detect the second detection voltage applied to the
input port as a first humidity indicating voltage, and render the
second output port the high impedance, apply the alternating
voltage across the first output port and the third output port, and
detect the second detection voltage applied to the input port as a
second humidity indicating voltage, and wherein the controller is
further configured to: execute a judgment process wherein judgment
is made as to which of the first humidity indicating voltage and
the second humidity indicating voltage is relevant to use in
determining the value of humidity upon comparison of the second
humidity indicating voltage with a threshold voltage.
12. The image forming device according to claim 10, wherein in the
second signal applying process, the controller is configured to:
render the third output port the high impedance, apply the
alternating voltage across the first output port and the second
output port and detect the second detection voltage applied to the
input port as a first humidity indicating voltage, and render the
second output port the high impedance, apply the output voltage
across the first output port and the third output port and detect
the second detection voltage applied to the input port as a second
humidity indicating voltage, and wherein the controller is further
configured to execute a judgment process wherein judgment is made
to determine which of the first humidity indicating voltage and the
second humidity indicating voltage is relevant to use as a basis
for outputting the humidity upon comparison of the first humidity
indicating voltage with a threshold voltage.
13. The image forming device according to claim 12, wherein the
first resistance change type-sensor operates as a humidity sensor,
the humidity sensor having a resistance characteristic such that
resistance of the humidity sensor decreases as humidity increases,
and the thermistor has a resistance characteristic such that
resistance of the thermistor decreases as temperature increases,
and wherein the controller is further configured to: detect the
first humidity indicating voltage under a condition where the first
output port is at the first voltage level and the second output
port is at the second voltage level lower than the first voltage
level, perform humidity detection using the first humidity
indicating voltage when the first humidity indicating voltage is
greater than the threshold voltage, and perform humidity detection
using the second humidity indicating voltage when the first
humidity indicating voltage is equal to or smaller than the
threshold voltage.
14. The image forming device according to claim 12, wherein the
first resistance change sensor operates as a humidity sensor, the
humidity sensor having a resistance characteristic such that
resistance of the humidity sensor decreases as humidity increases,
and wherein the controller is further configured to: detect the
second humidity indicating voltage under a condition where the
first output port is at the first voltage level and the third
output port is at the second voltage level lower than the first
voltage level, perform humidity detection using the first humidity
indicating voltage when the second humidity indicating voltage is
greater than the threshold voltage, and perform humidity detection
using the second humidity indicating voltage when the first
humidity indicating voltage is equal to or smaller than the
threshold voltage.
Description
CROSS REFERENCE TO RELATED APPLICATION
This application claims priority from Japanese Patent Application
No. 2013-062089 filed Mar. 25, 2013. The entire content of the
priority applications is incorporated herein by reference.
BACKGROUND
1. Field of the Invention
The present invention relates generally to a sensor device and a
method of using the same, and more particularly, to a sensor device
having a plurality of resistance change type sensors (or variable
resistance sensors) for sensing, for example, humidity and
temperature.
2. Description of the Related Art
Japanese Patent Application Publication No. 2009-180560 discloses a
sensor device having a detecting part and a controller, in which
the outputs of the detecting part are applied to the controller.
The detecting part includes a plurality of resistance change type
sensors. Each resistance change type sensor outputs a voltage
changeable depending upon the resistance of the sensor which in
turn is changeable depending upon a parameter to be detected, such
as humidity.
In this publication, the controller is provided with input
terminals configured to separately and individually receive each
output from each of the plurality of sensors. As such, the number
of input terminals of the controller needs to be increased as the
number of the sensors in the detecting part increases. However, it
is inconvenient for the sensor device to replace or re-design the
controller so as to be capable of accepting an increased number of
outputs from the increased number of sensors.
SUMMARY
In view of the foregoing, it is an object of the invention to
provide a sensor device having a plurality of resistance change
type sensors, in which the number of lines for transmitting the
sensor outputs does not need to be changed even if the number of
sensors contained in the sensor device is increased.
In order to achieve the above and other objects, the invention
provides according to one aspect, a sensor device that may include
a first resistance change type sensor, a second resistance change
type sensor, a fixed resistor, and a controller. The first
resistance change type sensor has a first terminal and a second
terminal and configured to detect a first parameter, such as
temperature. The second resistance change type sensor has a third
terminal and a fourth terminal connected to the first terminal and
configured to detect a second parameter, such as humidity. The
fixed resistor has a fifth terminal and a sixth terminal connected
to both the first terminal and the fourth terminal. The controller
has a first output port connected to the second terminal, a second
output port connected to the third terminal, a third output port
connected to the fifth terminal, and an input port connected to all
of the first terminal, the fourth terminal and the sixth terminal.
The controller may be configured to execute a first signal applying
process, a first detection process, a second signal applying
process, a second detection process, and a parameter detection
process in the stated order.
In the first signal applying process, the first output port is
rendered high impedance, and a predetermined voltage is applied
across the second output port and the third output port. The
predetermined voltage may be such a waveform that a first voltage
level and a second voltage level are alternately changed.
In the first detection process, a first detection voltage applied
to the input port is detected when the second output port is at the
first voltage level and the third output port is at the second
voltage level during execution of the first signal applying
process.
In the second signal applying process, one of the second output
port and the third output port is rendered high impedance. The
predetermined voltage is applied across the first output port and
remaining one of the second output port and the third output
port.
In the second detection process, a second detection voltage applied
to the input port is detected when the first output port is at the
first voltage level and the second output port or third output port
whichever is not rendered high impedance is at the second voltage
level during execution of the second signal applying process.
In the parameter detection process, a value of the first parameter
is determined using the first detection voltage and the second
detection voltage.
According to another aspect of the invention, there is provided an
image forming device that may include an image forming portion
configured to form an image on an object based on image data, and
the sensor device described above.
According to still another aspect of the invention, there is
provided a method of detecting humidity. To implement the method,
it is advisable to use a first series connection circuit connecting
in series a thermistor and a fixed resistor via a node, a second
series connection circuit connecting in series a resistance change
type humidity sensor and the thermistor via the node, and a third
series connection circuit connecting in series the resistance
change type humidity sensor and the fixed resistor via the
node.
The method may include a temperature detecting process, a first
humidity detecting process, a second humidity detecting process,
and a judgment process.
In the temperature detecting process, a predetermined voltage is
applied across the first series connection circuit to detect a
first voltage indicative of a temperature through the node. In the
first humidity detecting process, the predetermined voltage is
applied across the second series connection circuit to detect a
second voltage indicative of a first humidity through the node. In
the second humidity detecting process, the predetermined voltage is
applied across the third series connection circuit to detect a
third voltage indicative of a second humidity through the node. In
the judgment process, the first voltage is compared with a
reference voltage and judgment is made, based on a comparison
result, to determine which of the second voltage and the third
voltage is relevant to use as a basis for outputting the
humidity.
BRIEF DESCRIPTION OF THE DRAWINGS
The particular features and advantages of the invention as well as
other objects will become apparent from the following description
taken in connection with the accompanying drawings, in which:
FIG. 1 is a schematic vertical cross-sectional view showing a color
laser printer according to one embodiment of the invention.
FIG. 2 is a block diagram showing an electrical arrangement of the
printer shown in FIG. 1.
FIG. 3 is a graphical representation showing a relationship between
humidity values and detection voltages from a first circuit
configured from a humidity sensor and a thermistor connected in
series under varying environmental temperatures.
FIG. 4 is a graphical representation showing a relationship between
humidity values and detection voltages from a second circuit
configured from a humidity sensor and a fixed resistor connected in
series under varying environmental temperatures.
FIG. 5 is an enlarged graphical representation showing a low
humidity region in the graph of FIG. 3.
FIG. 6 is an enlarged graphical representation showing a low
humidity region in the graph of FIG. 4.
FIG. 7 is a flowchart illustrating a humidity detection
process.
FIG. 8 is a table showing a printer port status in each of various
detection modes to be selectively executed in the humidity
detection process.
FIG. 9 a timing chart for explaining the humidity detection
process.
DETAILED DESCRIPTION
One embodiment of the invention will be described with reference to
the accompanying drawings.
<Printer's Overall Structure>
FIG. 1 is a vertical cross-sectional view of a printer 1, which is
one of image forming devices, according to one embodiment of the
invention. As shown in FIG. 1, the printer 1 is a direct-transfer,
tandem type color laser printer capable of forming a full-color
image using four kinds of color toner of yellow, magenta, cyan and
black.
A print medium storage tray 14 is accommodated in a casing 12 of
the printer 1 and disposed in the lower portion thereof. A plenty
of sheet-type print media 16, such as sheets of paper, is stacked
in the tray 14. The tray 14 is capable of being drawn out of the
casing 12 for the user to supplement the print media 16. Upon
completion of supplementing the print media 16, the tray 14 is
returned to the right position within the casing 12. The print
media stacked in the tray 14 is urged against a pickup roller 28 by
a pressing plate 18 upwardly biased by a spring. In accordance with
rotations of the pickup roller 28, the uppermost print medium 16 is
fed toward a nip between a pair of conveying rollers 22 and further
away toward a nip between a pair of registration rollers 24. The
registration rollers 24 hold the print medium 16 until it is time
for it to be released, and correct the orientation of an obliquely
conveyed print medium 16. The print medium 16 having released from
the registration rollers 24 is conveyed further toward a conveying
section 30.
The conveying section 30 includes a pair of support rollers 32, 34,
an endless belt 36, and a plurality of transfer rollers 37 (four in
this embodiment). The endless belt 36 is wound around the
spaced-apart two support rollers 32, 34 with taut. The transfer
rollers 37 are juxtaposed along the print medium conveying
direction at equi-pitch inside the endless belt 36. The support
rollers 32, 34 are coupled to a motor (not shown) and thereby
rotated counter-clockwise, so that the upper part of the endless
belt 36 is moved leftward and the lower part thereof rightward.
An image forming unit 40 is disposed above the upper part of the
endless belt 36, and includes a scanning section 42 and a process
section 44. The process section 44 includes four sets of process
units corresponding to four kinds of color toner. Each process unit
includes a photosensitive drum 48, a developing cartridge 46, and a
charger 45. The charger 45 uniformly charges the peripheral surface
of the photosensitive drum 48 to positive polarity. Color toner is
contained in the developing cartridge 46 and a developing roller 47
is rotatably disposed in the developing cartridge 46. A developing
bias voltage is applied to the developing roller 47 by a high
voltage power supply 80 (see FIG. 2). The developing roller 47
applied with the developing bias voltage supplies toner contained
in the developing cartridge 46 to the photosensitive drum 48.
The scanning section 42 is disposed above the process section 44.
The scanning section 42 is configured to irradiate a laser beam L
onto the photosensitive drum 49 based on color-based image data fed
from a RAM 46 under the aegis of a central processing unit 62 (see
FIG. 2) which will hereinafter be referred to as "CPU 62". As a
result of laser beam irradiation, an electrostatic latent image is
formed on the surface of the photosensitive drum 48. The
electrostatic latent image thus formed corresponds to an image to
be formed on the print medium 16. The latent image is developed by
the toner supplied by the developing roller 47, and a visible toner
image is formed thereon.
As the photosensitive drum 48 rotates, the toner image formed
thereon reaches and passes a transfer position between the
photosensitive drum 48 and the endless belt 36. The toner image is
transferred on the print medium 16 when a transfer bias voltage is
applied to the transfer roller 37. The transfer roller 37 is
rotatably disposed in confrontation with the photosensitive drum 48
with the upper part of the endless belt 36 interposed therebetween.
As the print medium 16 on the endless belt 36 moves, four color
toner images are sequentially transferred on the print medium 16 so
as to be superposed one on the other. In this manner, a full-color
toner image is formed on the print medium 16 and is then thermally
fixed by a thermal fixing device 49. The print medium 16 on which
the color image is formed is conveyed and discharged by a pair of
conveying rollers 26 out to the casing 12 and placed on a discharge
tray 38 formed on the upper surface of the casing 12. In the
printer 1 shown in FIG. 1, the image forming unit 40 corresponds to
an image forming portion configured to form an image on an object
based on image data provided in an image forming device.
Slits 12A and 12B are formed at upper positions of the rear wall of
the casing 12 so as to be in fluid communication with external
environment. The positions where the slits 12A and 12B are formed
are not limited to the above-described positions but may be formed
in other appropriate positions. A humidity sensor 54 and a
temperature sensor 56 are disposed inside the casing 12 and in
positions where the slits 12A and 12B are formed. The humidity
sensor 54 is provided for sensing ambient humidity through the slit
12A and the temperature sensor 56 for sensing ambient temperature
through the slit 12B. These two slits 12A and 12B are formed in
adjacent positions so that the ambient air subject to sensing is
substantially the same. In this embodiment, a thermistor is used as
the temperature sensor. As is known in the art, the thermistor has
a temperature-dependent resistance. Also, a resistor having a
humidity-dependent resistance is used as the humidity sensor. The
temperature sensor 56 using the thermistor is one example of a
first temperature-dependent resistance change type sensor and the
humidity sensor 54 is one example of a second humidity-dependent
resistance change type sensor. The CPU 62 sets the transfer bias
voltage to be applied to the transfer rollers 37 based on the
ambient humidity and ambient temperature detected by the humidity
sensor 54 and the temperature sensor 56.
<Electrical Arrangement of Sensor Device Provided in
Printer>
FIG. 2 shows, in a block form, an electrical arrangement of a
sensor device 10 provided in the printer 1 and the parts of the
printer 1 subject to control based on the outputs from the sensor
device 10. The sensor device 10 includes an application specific
integrated circuit 60 (hereinafter referred to as "ASIC 60") for
controlling the scanning section 42 and the high voltage power
source 80 which in turn controls the chargers 45, developing
rollers 47 and transfer rollers 37.
The ASIC 60 is applied with drive voltage Vcc from an external
power source and connected to ground. The ASIC 60 includes the CPU
62, ROM 64, RAM 66, drive circuit 68, first output circuit 72,
second output circuit 74, third output circuit 76,
analog-to-digital converter 78, first to third output ports P1, P2,
P3, and input port Pin, all of which are connected to a bus 70.
Also, the scanning section 42 and the high voltage power source 80
are connected to the bus 70. The ASIC 60 illustrated in FIG. 2 is
one example of a controller contained in the printer 1.
The ROM 64 stores various programs and a table 65 used for
controlling the operation of the printer 1. The CPU 62 controls the
various parts of the printer 1 in accordance with the programs
retrieved from the ROM 64. The table 65 includes a first humidity
sensing table 65A and a second humidity sensing table 65B. The CPU
62 refers to the table 65 when detecting the ambient humidity.
The drive circuit 68 is connected to a motor (not shown) and
transmits pulse signals thereto in response to instructions fed
from the CPU 62. The motor rotates in accordance with the pulse
signals fed from the drive circuit 68. Rotations of the motor
rotate medium conveying rollers, and rotations of the rollers
convey the print medium 16 along the conveying path.
The ASIC 60 includes a first signal output circuit 72, a second
signal output circuit 74 and a third signal output circuit 76. The
first to third signal output circuits 72, 74, 76 apply first to
third output signals AC1, AC2, AC3 to the first to third output
ports P1, P2, P3 respectively, in response to the instructions from
the CPU 62. As shown in FIG. 9, each of the first to third output
signals AC1, AC2, AC3 is a rectangular waveform signal changing
between a high (H) level voltage equal to the power source voltage
Vcc and a low (L) level voltage equal to the ground voltage (GND)
every half cycle (180 degrees). In this embodiment, the power
source voltage Vcc, i.e., H level, is 3.3 volts, and the ground
voltage (GND), i.e., L level, is 0 (zero) volt.
The first output signal AC1 and the second output signal AC2 are
reversed phase signals such that the two signals are the same
waveform signals but the phase of one signal is delayed or advanced
by 180 degrees with respect to the other signal. More specifically,
the rising edge of the first output signal AC1 is in coincidence
with the falling edge of the second output signal AC2, and the
falling edge of the first output signal AC1 is in coincidence with
the rising edge of the second output signal. The H level duration
of the first output signal AC1 is equal to the L level duration of
the second output signal, and inversely the L level duration of the
first output signal AC1 is equal to the H level duration of the
second output signal AC2. The same is true with respect to the
relation between the second output signal AC2 and the third output
signal AC3 and between the third output signal and the first output
signal AC1.
The humidity sensor 54 and the temperature sensor 56 are connected
in series between the first output port P1 and the second output
port P2 as shown in FIG. 2. In such a configuration, when the first
output signal AC1 is at the H level and the second output signal
AC2 is at the L level, the voltage at the first terminal 54a of the
humidity sensor 54 is higher than the voltage at the second
terminal 54b of the humidity sensor 54. In this condition, a
positive polarity divided voltage is developed between the first
terminal 54a and the second terminal 54b of the humidity sensor 54.
Inversely, when the first output signal AC1 is at the L level and
the second output signal AC2 is at the H level, the voltage at the
first terminal 54a of the humidity sensor 54 is lower than the
voltage at the second terminal 54b of the humidity sensor 54. In
this condition, a negative polarity divided voltage is developed
between the first terminal 54a and the second terminal 54b of the
humidity sensor 54. As such, the positive and negative polarity
voltages with the same voltage in absolute value are alternately
applied to the humidity sensor 54. In other words, the humidity
sensor 54 senses the ambient humidity while being applied with the
AC voltage. Each of the output signals AC1, AC2, AC3 is not limited
to the above-described rectangular waveform but may be other form,
such as trapezoidal waveform.
The AC type voltage application to the humidity sensor 54 is more
advantageous than a DC type voltage application thereto. The
humidity sensor of the type in which the resistance of the humidity
sensor changes depending upon humidity typically includes a
humidity sensitive material, such as an electrically conductive
high molecular membrane in which ions are allowed to be movable
therein. The DC type voltage application to such a sensor yields
electrical polarization in the high molecular membrane, which
hinders accurate measurements of the resistance of the sensor.
As shown in FIG. 2, the sensing part 50 includes the humidity
sensor (HUM) 54, the thermistor (THM) 56 serving as the temperature
sensor, and a fixed resistor 58. The humidity sensor 54 and the
thermistor 56 are connected in series across the first output port
P1 and the second input port P2. Specifically, the humidity sensor
54 has a first terminal 54a connected to the first output port P1
and a second terminal connected to the first terminal 56a of the
thermistor 56 via a node SP. The thermistor 56 has a second
terminal 56b connected to the second output port P2.
The thermistor 56 and the fixed resistor 58 are connected in series
across the second output port P2 and the third output port P3.
Specifically, the second terminal 56b of the thermistor 56 is
connected to the second output port P2, the first terminal 56a of
the thermistor 56 is connected to the first terminal 58a of the
fixed resistor 58 via the node SP, and the second terminal 58b of
the fixed resistor 58 is connected to the third output port P3.
The first output port P1 of the ASIC 60 is connected to the first
terminal 54a of the humidity sensor 54, the second output port P2
of the ASIC 60 is connected to the second terminal 56b of the
thermistor 56, and the third output port P3 is connected to the
second terminal 58b of the fixed resistor 58. Further, the input
port Pin of the ASIC 60 is connected to the node SP connecting the
humidity sensor 54, thermistor 56 and fixed resistor 58.
With the above-described configuration, the sensing part 50
includes a temperature sensing circuit 51 in which the thermistor
56 and the fixed resistor 58 are connected in series across the
second and third output ports P2 and P3, a first humidity sensing
circuit 52A in which the humidity sensor 54 and the thermistor 56
are connected in series across the output ports P1 and P2, and a
second humidity sensing circuit 52B in which the humidity sensor 54
and the fixed resistor 59 are connected in series across the output
ports P1 and P3.
In each of the above-described three sensing circuits, the divided
voltage developed across the humidity sensor 54 or the thermistor
56 or across the fixed resistor 58 appears at the node SP and is
applied to the input port Pin of the ASIC 60. The voltage supplied
from the temperature sensing circuit 51 is applied to the input
port Pin as a detection voltage AD1, the voltage supplied from the
first humidity sensing circuit 52A as a detection voltage AD2, and
the voltage supplied from the second humidity sensing circuit 52B
as a detection voltage AD3. The analog-to-digital converter 78 of
the ASIC 60 separately receives the detection voltages AD1, AD2 and
AD3 at a sampling timing specified by the CPU 62 (see FIG. 9). The
analog-to-digital converter 78 converts the detection voltages in
the form of an analog signal to a digital signal.
The humidity sensor 54 has a temperature-dependent
humidity-versus-resistance characteristic (see FIGS. 3 and 4). For
example, the humidity sensor 54 has such a characteristic that it's
resistance changes from 10 Mega-Ohm to 1 Ohm with respect to the
change in relative humidity in a range from 10 to 80% RH and the
change in temperature in a range from 5 to 45 degrees Celsius.
Hereinafter, the "relative humidity" will simply be referred to as
"humidity" and its unit will be expressed with "%". The resistance
of the humidity sensor 54 is, for example, about 50 Ohm with the
humidity of 50% and the temperature of 25 degrees Celsius. The
humidity sensor 54 used in this embodiment exhibits a negative
resistance property with respect to both humidity and temperature.
Specifically, the humidity sensor 54 exhibits such a characteristic
that an increase in humidity results in a decreased resistance, and
an increase in temperature results in a decreased resistance. As
such, the resistance of the humidity sensor 54 is relatively high
under low-temperature/low-humidity whereas the resistance of the
humidity sensor 54 is relative low under
high-temperature/high-humidity.
The thermistor 56 has a negative temperature coefficient (NTC), so
that the resistance of the thermistor 56 decreases as the
temperature increases and the resistance of the thermistor 56
increases as the temperature decreases. For example, the resistance
of the thermistor 56 decreases from 3500 Kilo-Ohm to 44 Kilo-Ohm
attendant to the temperature increase from minus 10 to 80 degrees
Celsius. In this embodiment, the fixed resistor 58 has a resistance
of 680 kilo-Ohm which is roughly equal to the resistance of the
thermistor 65 (470 Kilo-Ohm) at 25 degrees Celsius. The fixed
resistor 58 needs to be selected to have a relevant resistance
falling within a selected range to optimize the temperature
detection accuracy. The above-noted resistances of the thermistor
56 and the fixed resistor 58 are one example to gain high humidity
detection accuracy under low-temperature/low-humidity circumstance.
In performing the humidity detection, selection of the thermistor
56 and the fixed resistor 58 need to be made depending upon the
temperature and humidity detection circumstance in order to
optimize the humidity detection accuracy.
<Humidity Detection>
Next, a humidity sensing will be described while referring to FIGS.
3 to 9.
Referring to FIGS. 3 to 6, first and second humidity detection
characteristic curves will be described. The first humidity
detection characteristic curve is obtained by the first humidity
sensing circuit 52A in which the humidity sensor 54 and the
thermistor 56 are connected in series across the first and second
output ports P1 and P2 of the ASIC 60. The second humidity
detecting characteristic curve is obtained by the second humidity
sensing circuit 52B in which the humidity sensor 54 and the fixed
resistor 58 are connected in series across the first and third
output ports P1 and P3 of the ASIC 60. In this embodiment, either
one of the first and second humidity sensing circuits 52A and 52B
is selectively used for the reasons stated below.
The humidity sensor 54 exhibits a resistance characteristic such
that the resistance is fairly large under the
low-temperature/low-humidity circumstance. In order to increase the
detection accuracy, it is required that the counterpart resistor of
the serially connected humidity sensing circuit have a large
resistance to output a high level divided voltage across the
counterpart resistor. On the other hand, the resistance
characteristic of the humidity sensor exhibits that the resistance
is small under the high-temperature/high-humidity circumstance. In
order to increase the detection accuracy under such a circumstance,
it is required that the counterpart resistor of the serially
connected humidity sensing circuit have a small resistance to
output a high level divided voltage. As such, the use of the same
counterpart resistor makes it difficult to attain high detection
accuracy in both the low-temperature/low-humidity circumstance and
the high-temperature/high-humidity circumstance. To solve such a
difficulty, the thermistor 56 and the fixed resistor 58 are
selectively used as the counterpart resistor of the serially
connected humidity sensing circuit, whereby detection of the
humidity can be achieved with excellent accuracy regardless of the
degrees of temperature and humidity.
FIG. 3 shows a first humidity sensing characteristic to be detected
by the use of the first serially connected humidity sensing circuit
52A. This characteristic shows that the detection voltage AD2
developed across the thermistor 56 does not saturate in a range
except for the low-temperature/low-humidity range, so that
detection of humidity can be achieved with fairly good accuracy.
Particularly, in the high-temperature/high-humidity range, the use
of the first humidity sensing characteristic is more advantageous
in terms of detection accuracy than a second humidity sensing
characteristic shown in FIG. 4 which shows the characteristic to be
detected by the use of the second serially connected humidity
sensing circuit 52B.
On the other hand, in the low-temperature/low-humidity range, the
second humidity sensing characteristic is more advantageous than
the first humidity sensing characteristic in terms of detection
accuracy as can be seen from FIGS. 5 and 6. Because, in the
low-temperature/low-humidity range, the detection voltage AD3
developed across the fixed resistor 58 changes at a rate higher
than the detection voltage AD2 developed across the thermistor 56.
For the reasons stated above, in accordance with the embodiment,
depending upon the detection range of the humidity, the first
humidity detection voltage AD2 obtained from the first serially
connected humidity sensing circuit 52A and the second humidity
detection voltage AD3 obtained from the second serially connected
humidity sensing circuit 52B are selectively used to attain high
detection accuracy in both the low-temperature/low-humidity range
and the high-temperature/high-humidity range.
Data representing the humidity-versus-detection voltage
characteristic for each temperature is written in a first humidity
detection table 65A stored in the ROM 64. More specifically, the
first humidity detection data AD2 and the corresponding humidity
are stored in the ROM 64 in association with the temperature
detection voltage AD1. Similarly, data representing the
humidity-versus-detection voltage characteristic for each
temperature is written in a second humidity detection table 65B
stored in the ROM 64. Specifically, the second humidity detection
data AD3 and the corresponding humidity are stored in the ROM 64 in
association with the temperature detection voltage AD1. Further,
data representing the characteristic of the resistance of the
thermistor 56 and temperature may also be stored in the ROM 64. It
should be noted that the detection voltage AD1 corresponds to or
equivalent to the resistance of the thermistor 56.
The CPU 62 detects the humidity based on the temperature detection
voltage AD1 detected by the temperature detecting serially
connected circuit 51, the first humidity detecting voltage AD2, and
data written in the first humidity detection table 65A.
Specifically, the humidity can be obtained by designating the
temperature detecting voltage AD1 and the first humidity detecting
voltage AD2 on the first humidity detecting table 65A.
Alternatively, the CPU 62 detects the humidity while referring to
the temperature detecting voltage AD1, the second humidity
detecting voltage AD3, and the second humidity detecting table 65B.
Specifically, the humidity can be obtained by designating the
temperature detecting voltage AD1 and the second humidity detecting
voltage AD3 on the second humidity detecting table 65B.
The humidity detection voltages AD2 and AD3 on the axis of ordinate
in the graphs shown in FIGS. 3 to 6 correspond to the resistance of
the humidity sensor 54. Accordingly, the axis of ordinate in the
graphs can be understood as indicating the resistance of the
humidity sensor 54. In this embodiment, however, the humidity
detecting voltages AD2 and AD3 are the voltages appearing at the
node SP. More specifically, the voltage AD2 is the divided voltage
developed across the thermistor 56 in the serially connected
circuit of the humidity sensor 54 and the thermistor 56, and the
voltage AD3 is the divided voltage developed across the fixed
resistor 58 in the serially connected circuit of the humidity
sensor 54 and the fixed resistor 58 when the first output port P1
is at a H-level voltage. With such a circuit configuration, the
graphs shown in FIGS. 3 to 6 indicate that as the humidity
detecting voltages AD2 and AD3 become greater, the resistance of
the humidity sensor 54 becomes smaller.
Next, the humidity detecting process will be described while
referring to FIGS. 7 to 9. The humidity detecting process is
executed by the CPU 62 in accordance with the program stored in the
ROM 64. The program runs in response to a print instruction entered
by a user, for example. The humidity detecting process may not
necessarily be implemented by the user's print instruction but be
implemented at every predetermined interval during printing
operation.
As shown in FIG. 7, the CPU 62 first executes a temperature
detection mode (S10). In the temperature detecting mode, as shown
in FIGS. 8 and 9, the second output signal AC2 output from the
second output port P2 has an H-level duration and an L-level
duration which are alternately repeated. The third output signal
AC3 output from the third output port P3 has also an H-level
duration and an L-level duration which are alternately repeated.
The second and third output signals AC2 and AC3 are in phase with
each other but the level of one signal is in reversed relation with
that of the remainder. Specifically, when the signal AC2 is at the
H-level, the signal AC3 is at the L-level, and vice versa. Under
the temperature detection mode, the first output port P1 is held in
a high impedance state (Hiz). As shown in FIG. 9, the temperature
detecting mode is effected in the duration from t0 to t4 as shown
in FIG. 9.
In the sampling period at which the second output port P2 (the
second output signal AC2) is at the H-level and the third output
port P3 (third output signal AC3) is at the L-level, the
analog-to-digital converter 78 inputs the temperature detecting
voltage AD1 appearing at the node SP and converts the inputted
voltage AD1 to a digital value in accordance with the instructions
from the CPU 62. The CPU 62 instructs the RAM 66 to temporarily
store the digital value AD1. In this embodiment, the temperature
detection is carried out twice in succession and the two digital
values are averaged. The averaged digital value is used as a
temperature digital value AD1. The sampling periods to obtain two
temperature detection voltages are the time duration from t0 to t1
and the time duration from t2 to t3 in FIG. 9.
As shown in FIG. 7, the CPU 62 next executes a first humidity
detection mode (S20). In the first humidity detecting mode, as
shown in FIGS. 8 and 9, the first output signal AC1 output from the
first output port P1 has an H-level duration and an L-level
duration which are alternately repeated. The second output signal
AC2 output from the second output port P2 has also an H-level
duration and an L-level duration which are alternately repeated.
The first and second output signals AC1 and AC2 are in phase with
each other but the level of one signal is in reversed relation with
that of the remainder. Specifically, when the signal AC1 is at the
H-level, the signal AC2 is at the L-level, and vice versa. Under
the first humidity detection mode, the third output port P3 is held
in Hiz state. As shown in FIG. 9, the first humidity detecting mode
is effected in the duration from t4 to t8 as shown in FIG. 9.
In the sampling period at which the firsts port P1 (the first
output signal AC1) is at the H-level and the second port P2 (second
output signal AC2) is at the L-level, the analog-to-digital
converter 78 inputs the first humidity detecting voltage AD2
appearing at the node SP and converts the inputted voltage AD2 to a
digital value in accordance with the instructions from the CPU 62.
The CPU 62 instructs the RAM 66 to temporarily store the digital
value AD2. In this embodiment, the first humidity detection is
carried out twice in succession and the two digital values are
averaged. The averaged digital value is used as a first humidity
digital value AD2. The sampling periods to obtain two first
humidity detection voltages are time duration from t4 to t5 and
time duration from t6 to t7 in FIG. 9.
Next, the CPU 62 executes a second humidity detection mode (S30).
In the second humidity detecting mode, as shown in FIGS. 8 and 9,
the first output signal AC1 output from the first output port P1
has an H-level duration and an L-level duration which are
alternately repeated. The third output signal AC3 output from the
third output port P3 has also an H-level duration and an L-level
duration which are alternately repeated. The first and third output
signals AC1 and AC3 are in phase with each other but the level of
one signal is in reversed relation with that of the remainder.
Specifically, when the signal AC1 is at the H-level, the signal AC3
is at the L-level, and vice versa. Under the second humidity
detection mode, the second output port P2 is held in Hiz state. As
shown in FIG. 9, the second humidity detecting mode is effected in
the duration from t8 to t12 as shown in FIG. 9.
In the sampling period at which the firsts port P1 (the first
output signal AC1) is at the H-level and the third port P3 (third
output signal AC3) is at the L-level, the analog-to-digital
converter 78 inputs the second humidity detecting voltage AD3
appearing at the node SP and converts the inputted voltage AD3 to a
digital value in accordance with the instructions from the CPU 62.
The CPU 62 instructs the RAM 66 to temporarily store the digital
value AD3. In this embodiment, the second humidity detection is
carried out twice in succession and the two digital values are
averaged. The averaged digital value is used as a second humidity
digital value AD3. The sampling period to obtain two second
humidity detection voltages is time duration from t8 to t12. in
FIG. 9.
In the sampling period at which the first port P1 (the first output
signal AC1) is at the H-level and the third port P3 (third output
signal AC3) is at the L-level, the analog-to-digital converter 78
inputs the second humidity detecting voltage AD3 appearing at the
node SP and converts the inputted voltage AD3 to a digital value in
accordance with the instructions from the CPU 62. The CPU 62
instructs the RAM 66 to temporarily store the digital value AD3. In
this embodiment, the second humidity detection is carried out twice
in succession and the two digital values are averaged. The averaged
digital value is used as a second humidity digital value AD3. The
sampling periods to obtain two second humidity detection voltages
are time duration from t8 to t9 and time duration from t10 to t11
in FIG. 9.
Then, the CPU 62 determines whether the first humidity detecting
voltage AD2 detected under the first humidity detecting mode is
smaller than a threshold voltage Vth (S40). As shown in FIGS. 3 and
4, both the first and second humidity detecting characteristics can
provide good detection accuracy in the mid-range of humidity and
temperature, or normal humidity and normal temperature. Therefore,
the threshold voltage Vth is selected from a voltage range
corresponding to the normal temperature and normal humidity. For
example, the threshold voltage Vth is set to 1.5 volts.
When determination is made so that the first humidity detecting
voltage AD2 is smaller than the threshold voltage Vth, e.g., 1.5
volts, (S40:YES), the CPU 62 detects the humidity based on the
digital value AD1 representing the detected temperature, the
digital value AD3 obtained under the second humidity detecting
mode, and the second humidity detection table 65B (S50). The second
humidity detection table 65B includes digital values AD1, digital
values AD3, and humidity values correlated to one another.
Specifically, with the second humidity detection table 65B, a
humidity value can be specified by designating one of the digital
value AD1 and one of the digital values AD3 given with respect to
the designated digital value AD1. The second humidity detection
table 65B outputs data representing the humidity value upon receipt
of data regarding the digital values AD1 and AD3. The CPU 62 can
thus detect and recognize the humidity. Based on the detected
humidity, the CPU 62 sets transfer bias applied to the transfer
section.
On the other hand, when determination is made so that the first
humidity detecting voltage AD2 is not smaller than the threshold
voltage Vth, that is, when the humidity detecting voltage AD2 is
equal to or larger than the threshold voltage Vth (S40: NO), the
CPU 62 detects the humidity based on the digital value AD1
representing the detected temperature, the digital value AD2
obtained under the first humidity detecting mode, and the first
humidity detection table 65A (S60). The first humidity detection
table 65A includes digital values AD1, digital values AD2, and
humidity values correlated to one another. Specifically, with the
first humidity detection table 65A, a humidity value can be
specified by designating one of the digital value AD1 and one of
the digital values AD2 given with respect to the designated digital
value AD1. The first humidity detection table 65A outputs data
representing the humidity value upon receipt of data regarding the
digital values AD1 and AD2. The CPU 62 can thus detect and
recognize the humidity.
As described, the CPU 62 refers to the first humidity detection
table 65A and obtains a humidity value using the temperature
detecting voltage AD1 and the first humidity detecting voltage AD2.
A humidity value under the current temperature can be detected with
a simplified humidity detection process in which all the jobs need
for the CPU 62 to implement are to detect the temperature detecting
voltage AD1 and the first humidity detecting voltage AD2 and to
refer to the first humidity detection table 65A.
In the embodiment described above, the voltage appearing at the
node SP is sampled twice in each mode and the averaged value is
used as the detected value. However, this is only an example and
the invention is not limited thereto. For example, sampling the
voltage appearing at the node SP may be sampled once the sampled
voltage may be used as the detected voltage. Or, the voltage
appearing at the node SP may be sampled twice or more and an
average value may be used as the detected voltage.
In the above-described embodiment, the sampling period is set to
durations of t0 to t1, t4 to t5, t8 to t9 in the time chart of FIG.
9. That is, sampling the voltages at the node SP is performed when
the second port is in H-level and the third port, L-level, when the
first port is in H-level and the second port, L-level, and when the
first port is in H-level, and the third port, L-level. However,
when sampling is to be performed is not limited to those described
above. For example, sampling may be performed when the second port
is in L-level and the third port, H-level, when the first port is
in L-level and the second port, H-level, and when the first port is
in L-level, and the third port, H-level (see FIG. 8). If the
sampling is performed at such timings, the sampled voltages are not
the same as those in the above-described embodiment. Accordingly,
the tables 65A and 65B need to be modified.
According to the sensor device described above, the voltage AD1
indicative of the temperature, and the voltages AD2 and AD3
indicative of the humidity under different temperature ranges are
detected in time-division manner through a common input terminal
Pin. Thus, the number of input terminals does not need to be
increased unlike the conventional sensor device.
Further, the humidity sensor 54 according to the above-described
embodiment uses the temperature-dependent resistance versus
humidity characteristics as shown in FIGS. 3 and 4 to obtain the
voltage AD1 using the thermistor 54, the voltage AD2 indicative of
the first humidity detected under the first humidity detecting
mode, and the voltage AD3 indicative of the second humidity
detected under the first humidity detecting mode. Thus, the
humidity sensor 54 described above can correct the influence of
temperature imposed thereupon in providing the detection results.
This means that the detection accuracy is improved.
In the above-described embodiment, the first humidity detecting
mode is implemented in such a manner that the third port P3 is held
in high impedance state and the output voltages AC are applied to
the first and second ports P2 and P3 to detect the voltage AD2
applied to the input port Pin. The second humidity detecting mode
is implemented in such a manner that the second port P2 is held in
high impedance state and the output voltages AC are applied to the
first and third ports P1 and P3 to detect the voltage AD3 applied
to the input port Pin. Upon detection of the voltages AD2 and AD3,
a judgment process (S40) is executed to determine which detected
voltage is to be used for providing the humidity by comparing the
voltage AD2 with the threshold value, e.g., 1.5 volts. As such,
depending upon the value of the detection voltage AD2, used is
either the first humidity detecting characteristic as shown in FIG.
3 and provided by the first humidity detection serially connected
circuit 52A or the second humidity detecting characteristic as
shown in FIG. 4 and provided by the second humidity detection
serially connected circuit 52B whichever is appropriate. In other
words, the humidity sensor 54 uses two different characteristics
that provide different humidity values corresponding to the
detected voltage (or resistance). As such, the above-described
embodiment can broaden a dynamic range (detection resolution) in
the detection voltages in a low-temperature/low-humidity range and
high-temperature/high-humidity range, for example. Consequently,
detection of the humidity with high accuracy can be
accomplished.
In the above-described embodiment, the humidity is finally provided
based either on the detection voltage AD2 if the latter is equal to
or larger than the threshold value (e.g., 1.5 volts) or on the
detection voltage AD3 if the latter is smaller than the threshold
value. In this way, one of the voltages AD2 and AD3 detected
following the first and second humidity detecting characteristics,
respectively, is selectively used, so that the resolution of the
detected voltages can be increased. As a result, the detection
accuracy of the humidity sensor 54 can be improved over an entire
detectable range from a low-temperature/low-humidity point to the
high-temperature/high-humidity point.
Although the present invention has been described with respect to a
specific embodiment, it will be appreciated by one skilled in the
art that a variety of changes and modifications may be made without
departing from the scope of the invention.
For example, in the above-described embodiment, while the detection
voltage AD2 obtained in the first humidity detecting mode (S20) is
compared with the threshold value Vth to determine which detection
voltage AD2 or AD3 is used (S40) and the humidity is finally
obtained based on the selected voltage. The invention is not
limited to the above-described procedure. Instead, the detection
voltage AD3 obtained through the second humidity detecting mode
(S30) may be compared with the threshold value Vth. Either the
detection voltage AD2 or the detection voltage AD3 may be selected
based on the comparison results and the humidity may be provided
based on the selected detection voltage AD2 or AD3. When the
detection voltage AD3 is larger than the threshold value Vth, the
humidity detection is performed using the detection voltage AD2
whereas when the detection voltage AD3 is equal to or smaller than
the threshold value Vth, the humidity detection is performed using
the detection voltage AD3. Such procedure can also improve the
detection resolution similar to the above-described embodiment. As
a result, the detection accuracy of the humidity sensor 54 can be
improved over an entire detectable range from a
low-temperature/low-humidity point to the
high-temperature/high-humidity point.
In the above-described embodiment, the first humidity detecting
mode (S20) and the second humidity detecting mode (S30) are
executed and then the processes in S40 onward are executed in the
humidity detecting process. The invention is not limited to such a
procedure. Instead, only the temperature detecting mode (S10 and
the first humidity detecting mode (S20) may be executed and the
processes in S40 onward may be dispensed with, if the detection
accuracy in the low-temperature/low-humidity range or
high-temperature/high-humidity range is not so important.
Alternatively, only the temperature detecting mode (S10) and the
second humidity detecting mode (S30) may be executed but other
processes may be dispensed with.
In the above-described modifications, the humidity sensor having a
temperature-dependent resistance characteristic uses the resistance
versus humidity characteristic in relation to the temperature or
the detection voltage AD1 detected by the thermistor and also uses
the detection voltage AD2 or AD3 obtained through the second
detecting process using the resistance of the humidity sensor.
Accordingly, the detection accuracy of the humidity sensor can be
improved. In the above instances, either one of the first and
second humidity detection tables 65A and 65B can be dispensed
with.
Although the above-described embodiment describes the sensor device
provided in the device having a printing function, the present
invention is not only applicable thereto but applicable to, for
example, a multi-function peripheral having at least one of
printing function, scanner function, copying function, facsimile
transmission/reception function and so on. The device to which the
invention is applicable may not be provided with the printing
function. The sensor device according to the invention is
applicable to various kinds of devices which perform various kinds
of adjustments based on measured results of various parameters
including temperature and humidity.
While the above-described embodiment uses the thermistor and
humidity sensor as examples of resistance change type sensors, the
invention is not limited to the use of such specific devices. Other
resistance change type sensors, such as distortion gauge, volume
sensor, CdS cell illumination sensor, may be employed to detect
parameters other than the humidity. In other words, the sensor
device according to the invention is not limited to those for
detecting temperature and humidity.
The above-described embodiment exemplifies a printer 1 having a
single ASIC 60 as an example of a controller and a single CPU 62
contained in the ASIC 60 executes various processes. The invention
is not limited to use the single ASIC but may use a plurality of
CPUs and/or ASICs to execute the required processes. Further, the
controller may not be configured from the ASIC having the CPU 62 by
may be configured by a CPU and a plurality of peripheral circuits
connected thereto.
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